Marine Weather Net

Straits of Florida from west end of Seven Mile Bridge to south of Halfmoon Shoal out 20 to 60 NM Marine Forecast


OVERNIGHT

S
WINDS
10
KNOTS

FRIDAY

SW
WINDS
10
KNOTS

FRIDAY NIGHT

S
WINDS
5 - 10
KNOTS

SATURDAY AND SATURDAY NIGHT

VARIABLE
WINDS
5 KNOTS

The Marine Weather Forecast In Detail:
GMZ074 Forecast Issued: 1023 PM EDT Thu Sep 24 2020

Overnight...Southeast To South Winds Near 10 Knots. Seas 2 To 4 Feet. Scattered Showers And Isolated Thunderstorms.
Friday...South To Southwest Winds Near 10 Knots. Seas 2 To 3 Feet. Numerous Showers And Isolated Thunderstorms In The Morning, Then Scattered Showers And Isolated Thunderstorms.
Friday Night...South Winds 5 To 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.
Saturday And Saturday Night...Variable Winds Near 5 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.
Sunday...Northeast To East Winds 5 To 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.
Sunday Night...East Winds 5 To 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.
Monday And Monday Night...East To Southeast Winds 5 To 10 Knots. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.
Tuesday And Tuesday Night...Variable Winds 5 To 10 Knots. Seas Around 1 Foot. Scattered Showers And Isolated Thunderstorms.
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Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005
1023 PM EDT Thu Sep 24 2020

Gentle and moderate southeast breezes will continue to ease through Friday morning. Thereafter, a weak pressure pattern will result in light to gentle breezes this weekend and early next week.

Gulf Stream
The Approximate Shoreward Edge of the Gulf Stream as of September 22...
- 5 NM South of Dry Tortugas Light...on Loggerhead Key.
- 8 NM South of Cosgrove Shoal Light...off the Marquesas Keys.
- 4 NM South of Sand Key Light...off Key West.
- 6 NM South of Looe Key...off Big Pine Key.
- 6 NM South of Sombrero Key Light...off Marathon.
- 1 NM Southeast of Alligator Reef Light...off Islamorada.
- 2 NM Southeast of Molasses Reef Light...off Key Largo.
- 1 NM East of Carysfort Reef Light...off Ocean Reef.
Area Forecast Discussion
National Weather Service Key West FL
1028pm EDT Thu September 24 2020

The most impactful short-term issue will again be saltwater flooding on Friday morning. The difference between tide table predictions and observed tide levels is running around an uncommonly high 1.3 feet at Key West. Given this trend, tides will peak on Friday morning at levels similar to early this morning. High water will be most noticeable from about 4-9 am, with areas of standing water lingering for a few hours after the tide falls. A Coastal Flood Advisory is in effect for the entire Keys until 12 Noon.

Our 1000-700 mb layer flow has turned southerly over the past 24 hours, thanks in part to the northeast movement of Post-Tropical Cyclone Beta across west-central and northern Alabama this evening. The turn to southerly flow wiped out yesterday's dry air mass impressively quick. Since last evening, the 00z KEY sounding showed an increase in PW values (Precipitable Water values) from 1.47" to 2.4".

Against the backdrop of rich and deep moisture, a small-scale trough is lifting north across the Keys. This is adding lift to the very moist and moderately unstable air mass. Later Friday, that trough will move northward to Central Florida. So we will lose the larger-scale lift by Friday evening. Light and variable low-level flow over the weekend will let differential heating and convective outflows be the main driver of convective development. Low chance Probability of Precipitation will cover the weekend weather nicely.

Marine
Winds will gradually veer from southeast to south overnight, as a northward-moving trough cross the waters.

Pressure gradients will become quite weak from Friday night through the weekend, leaving light and variable winds over the Keys waters.

NOAA Key West FL Office: Watches - Warnings - Advisories
FL...Coastal Flood Advisory until noon EDT Friday for FLZ076>078.

GM...None.